Steer-By-Wire to Reach Production Vehicles

Taking a page from the world of aviation, Nissan Motor Co. plans to enter the "by-wire" world and control the steering of a future Infiniti vehicle with electronic signals.

The decision to bring steer-by-wire to a production vehicle is a major one for the automobile industry because it lays the foundation for eventual elimination of the mechanical components that now connect the driver to a vehicle's tires.

"There are a lot of advantages to this," Infiniti spokesman Kyle Bazemore told Design News. "It enhances the driving experience. And in the future, after consumer acceptance of the technology, we could theoretically do away with the mechanicals and save the weight."

Nissan's next-generation steering employs a steering angle sensor at the steering wheel, three ECUs for control, electric motors to power the rack, and a steering force actuator near the driver to retain the vehicle's "steering feel."

The next-generation steering system, as Nissan calls it, works by endowing the steering wheel with sensors that read the desired steering angle. Data from the sensors is sent to one of three electronic control units (ECUs), which activate electric motors on the vehicle's steering rack. In contrast, conventional steering uses a direct mechanical connection to the rack-and-pinion.

In truth, the new Nissan system won't eliminate the mechanical connection to the driver. Instead, it will use the mechanical connection as a redundant system, only in cases of extreme emergency. If, for example, a power supply conks out or all of the ECUs fail, it will employ a back-up clutch to mechanically connect the steering wheel to the tires. "The clutch is disengaged 999,999 times out of a million," Bazemore told us. "But the steering shaft is still there, just in case."

Nissan said steer-by-wire will enhance the driving experience. When it reaches the market late next year, it will eliminate some of the vibration from rough road surfaces and it will minutely adjust tire angles to compensate for crosswinds and sloped surfaces. At the same time, it will enable drivers to "feel" the road. Grip information, such as slipperiness, will be transferred back to a steering force actuator that will allow the steering wheel to retain some of its original feel. "Theoretically, you could have no steering feel at all, but that would not be good for drivers," Bazemore said. "That's why we dialed some -- but not all -- of the steering feel back into the system."

I would hope that the automakers would take into account when the vehicle might run out of fuel which unfortunately occurs quite a lot. At least with a vehicle with a current steering linkage, you can coast to the shoulder with some steering mobility. It would be terrible if your wheels locked in their current orientation and you could not nudge your vehicle out of traffic.

We have already tried fly-by-wire accelerators and they have proven failures. It is not just Toyota, but other cars as well that have accelerated far faster than the driver has wanted. Less well publicized is the fact fly-by-wire gas pedals also have numerous complaints for low idle as well. Cars simply are expensive or maintained well enough for these systems right now. Maybe in 30 years when the cost of the technoloy comes down, but I doubt, because there will still be far too many people who can't afford proper maintenance.

That's interesting, Chuck. If the redundant system is electronic, than it will have the same vulnerability if the electrical system goes out. I've experienced driving a car when the electricity goes out. The steering becomes more difficult, but you can still steer.

Maybe it could serve to make the car lighter, or reduce costs, but statements such as "Enable drivers to feel" the road" or "Enhance driving" just don't make any sense! How can you disconnect the driver from the road and put him behind a simulated steering wheel and yet claim that this will help the driver feel the road? Doesn't this sound like pure marketing nonsense?

You've got a point there, Rigby5. The thing with autos, rather than industrial vehicles is that test and maintenance practices will vary extremely widely. Commercial vehicles and aircraft have mandatory inspections, etc. The individual, on the other hand, might do only minimal inspection. What happens when there is a control failure in traffic? How do you safely get to a stop with no power?

Why is it car makers do not understand that buyers don't want to eliminate the mechanical systems. They don't want the accelerator, steering, or brakes to be fly by wire. If you actually told customers the truth, they would refuse to buy any of the cars with these systems. Andt that is because we all know these systems are bound to fail eventually, so are unacceptible in a car.

Didn't Nissan also give us the one big button to both start the engine and to stop it? Or at least go along with those who started that fad? Since they demonstrated poor judgement by doing that, why should I believe that their drive by wire is any smarter? An electrically assisted power steering system would be different, and they have been around in various applications since around 1980, or thereabouts.

Don't compare this idea with aircraft fly-by-wire systems because there is no comparison. The number one directive for aviation systems is safety, followed by longevity of service, also called reliability. The number one directive in the automotive industry is PROFIT from initial sales, and next is cheapness to manufacture. We all know that it is true, at least those with any automotive engineering experience. Aside from that, only qualified people are legally allowed to service aircraft, while anybody who can grasp a wrench is allowed to service cars.

In addition, as pointed out already, how can we expect that a cheapo electronic controller in an environment nastier than the navy salt spray test, will be more reliable than the present power steering systems. Ask your self: "When was the last time that you heard about a power steering system failing"? And when the do fail it is usually the loss of assistance rather than a loss of steering control. While that failure mode may make driving difficult for the weak and feeble, it is merely quite inconvenient for most of us.

When it comes to making it happen without a mechanical back-up, you can count me as one of those skeptical customers, ChasChas. Obviously, though, Nissan agrees with you, not me. Here's what they told me: "The mechanicals are there for driver confidence. In reality, it doesn't need to be there. But in the future, after consumer acceptance of this, the mechanicals could go away, saving us the extra weight." If I fully understood how the back-up system would work in the absence of the mechanicals, I might feel more confident. But they're not explaining that yet.

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